This invention relates to a method of dyeing effectively and uniformly yarns spun by fine spinning frames.
Heretofore, for dyeing or heat treatment of yarns spun by fine spinning frames, such as ring and mule spinning frames, the yarns are commonly rewound on bobbins for purposes of the dyeing process after once being wound up in the form of cone from the spun cops. It is usually necessary for the winding-up of a cone to combine a plurality of cops, since the amount of wound-up yarn in a cop is smaller than that in the cone.
In the rewinding of cop yarn, there may arise, depending upon the shape of the cop, a difference in the rewinding tension between the yarns in the outer and in the inner layers of a cop. As a result, if the cop yarns are to be directly rewound on dyeing bobbins, the cheeses will be formed with so-called "annual rings" on account of the alternately repeated high and low rewinding tensions and will lead to dyeing variation of the yarn. But, if the cop yarn is to be rewound at a regulated, constant tension in order to prevent the formation of the annual rings, it must be rewound at a tension in agreement with the maximum tension of the cop yarn. Such a high rewinding tension, however, leads to a high winding density, which will cause various troubles in the dyeing process.
It is widely known that soft winding is suitable for wound-up yarn to be dyed smoothly and advantageously, and dyeing and treatments under low winding densities by soft winding are studied and practiced in various areas. On the other hand, direct rewinding from spun cops, being impossible to effect soft winding as mentioned above, will lead to various difficulties in dyeing.
Therefore, it has been necessary to wind up the yarns once from cops to cones and then rewind them soft on bobbins for the dyeing process in consideration of wind-up density.